Loud-speaker motor unit



y 6. 1929- 1. M. CLEMENT ET 1. 1,721,480

LOUD SPEAKER MOTOR UNIT Filed Sept. 11, 1926 2 Sheets-Sheet 1 Ju y 1929-L. M. CLEMENT ET AL LOUD SPEAKER MOTOR UNIT Filed Sept. 11, 1926' 2Sheets-Sheet M 7. amounted Patented July 16, 1929.

UNITED STATES 1,721,480 PATENT OFFICE.

LEWIS M. CLEMENT, OF MOUNTAIN LAKES, NEW JERSEY, AND JOHN F. NIELSEN, OF

WINFIELD, NEW YORK, ASSIGNORS TO I.

A CORPORATION OF NEW YORK..

. 1. n. ANDREA, me, on NEW YORK, N. Y.,

LOUD-SPEAKER MOTOR UNIT.

Application filed September Our invention relates to operating units forloud speakers, particularly to units for operating sounding boards oracoustlc rad a tors for loud speakers usually employed wlth radioreceiving instruments.

One of the important elements enter ng into the faithful translation ofelectrical energy into sound waves is the unit for operating the; soundboard. It is lmportant,

therefore, to properly arrange and construct the elements of the unit tosecure the best results.

Our invention will be better understood by reading the followingdescription taken in connection with the accompanying drawings whichillustrate one embodiment. of our in vention, and in which:

Fig. 1 is a to plan view of the unit; .Fig. 2 is a si e elevation of theunit Fig. 3 is a front elevation of the unit; Fig.4 is a view on linesIVI-V- of Fig. 1; Fig. 5 is'a view on line VV of Fig. 1; Fig. 6 is asectional viewon line VI VI ofFig.3; p

Fig. 7 is a sectionalview on line a i1 +VII ofFig.2and

Fig. '8 is an enlarged viewshowing the soldered joints between thearmature 19, operating tube 24 and. member 25.

In the drawings the mounting plates 1 and 2 are the supporting means forthe unitand may be of any suitable material, preferably of brass oraluminum. As best shown in Fig. 6, these plates support the unitby bolts3 and 4. The bolts 3 and 4 pass through the mounting plates 1 and 2 andnuts 5 and 6 hold them in position. The bolts 3 and;4 are-held in placeagainst the ends 7. and 8 of a permanent magnet by bolts-9 and 10. Polepieces 11, 12, 13 and 14 of magnetic material, preferably silicon steel,and also laminated if desired, are held firmly against the ends 7 and 8of the magnet by screws 15, 16, 17 and 18, which pass through faceplates 22 and 23. The pole pieces 11 .to 14 are ta cred, as shown inFig. 5. The narrow ends 0 .pole pieces 12 and 14 and of 11 and 15 areplaced close together and a magnetic armature .19 is held in positionbetween the pole pieces by a spring 20 which is carried by'bolts 21carried by the face plate 23.

Surrounding the armature 19 are coils 24 which are vheld'in positionbetween the pole pieces 11 0014. The bobbins upon which the 11, 1926.SerialNo. 134,779.

coils are wound are preferably molded and fit into the assembly and aresupported by the bolts 21. They are made so-that they do not touch thearmature or armature supporting spring.

Connected with the armature 19 is a tube 24 which is connected with amember 25 having a peculiar shape, which will now be described. There isa flattened part 26 on member 25 which is attached to the face .plate 23by screws 27 and washer 27*. This is a rigid support. To the end of themember 25 is attached the tube 24 and an operating rod 28 is attached tothe member 25 between the place o-f attachment of the tube 24 and thescrews 27. The place of connection of rod 28 to member 25 depends uponthe type of radiator used and the frequency at which maximum power is tobe delivered to the radiator. The member 25 vibrates in response tovibrations imparted by tube 24 and in order that there shall be aslittle resistance as possible to such vibrations the metal of member 25is aligned and arched transversely of the member 25 at 29', around whichpart the member vibrates. In order to render the member 25 as rigid aspossible from the part 29 to the end it is arched longitudinally alongthe line 30 from the point 29'to the free end of the member. By theconstruction shown the member 25 has a maximum rigidity, minimumresistance to movement and minimum mass. The driving tube 24 isflattened at its lower and upper ends so that the resistance to bendingcaused by armature 19 and member 25 will be a minimum,- while thelateral stiffness will be preserved. The metal of the tube 24 isflattened so that it lies in a plane atright angles to the longitudinalaxis ofthe armature. This is very lmportant as it improves theefiiciency and response characteristics by reducing the resistance tobending as described. It also prevents transverse vibration of the tubewhich would absorb energy at a vibr" Ion frequency. All of these aredesirable qualities in a unit of this type.

The vibrations of the armature 19 are transmitted through the member 25to the rod 28 and thenceto a sounding board or radiator of any desiredconstruction. The rod 28 has a covering 31 of dampening material toprevent lateral vibrations.

The face plates 22 and 23, the mounting plates 1 and 2'and the polepieces 11, 12, 13

and 14 are preferably all punch press parts. These are held together byscrew machine parts.

The transformer member 25 is made to combine stiffness with minimumweight and insure that bending will Occur onlyat 29.

The holes in the member 25 for the driving tube 24 are extruded as shownin order to form a cylindrical opening. The transformer member 25 isheld against its mounting plate by a washer 27 as shown. The armaturedriving rod which is made with two flat places, one near each end, toreduce the force required to bend the otherwise stiff rod when thearmature and transformer rotate around their bearings is held at bothends by soldering and riveting. One end of the rod is forced through anopening in the end of the armature and is then riveted and soldered. Theother end passes through the cylindrical opening in the member 25 and issoldered. This means of attaching the rod to the armature and member 25cuts down the mass and increases the efficiency in addition to givinggood joints. 1 i

In order to prevent lateral vibration of the armature driving rod, aspider 40 of rubher or other suitable material may be mount.- ed so thatif lateral vibrations start, they will be dampened by the spider.

The circuit for the electrical coils 24; is through wires 32 and 33which lead to con nectors 34: and 35 and thence to the ends of the coilswhich are in series, and their effects are additive. In the use of thedevice in a loud speaker for radio the wires 32 and 33 are connected ,tothe usual output circuit of the receiver.

.The supporting members 1 and 2 have elongated openings 36 and 37 forthe purpos of adjusting the position of the unit.

Our invention has many advantages which will be apparent to thoseskilled in the art.

e claim:

1. In a loud speaker motor unit, the combination of a permanent magnet,side members of non-magnetic material attached to the ends of saidmagnet, pole pieces for said magnet carried by said side members andheld firmly against the ends of said magnet, a resiliently supportedarmature between said pole pieces, two coils around said armature andmeans for connecting said armature with the dianhragm.

2. In a loud speaker motor unit, the combination of a permanent magnet,side members of non-magnetic material attached to the ends of saidmagnet, pole pieces for said magnet carried by said side members andheld firmly against the ends of said magnet, said pole pieces beingtapered and the tapered ends of the pieces in the same side of themagnet being adjacent each other, an armature resiliently supportedbetween said pole pieces and held in a neutral position, two coilssurrounding said armature and means connecting the armature with theloud speaker diaphragm.

3. In a loud speaker unit, the combination of a permanent magnet, fiatpole pieces held against each side face of each end of said magnet, aflat face plate of non-magnetic material bridging the ends of saidmagnet and lying alongside said pole pieces and mounting plates parallelwith said face plates.

4'. In a loud speaker unit, the combination of a permanent horseshoemagnet, magnetic pole pieces on the side faces of said magnet andextending into the open end of the horseshoe, said pole pieces beingpointed at their free ends, a face plate lying along each pair of polepieces, an armature having its ends extending between the pointed endsof said pole pieces, electrical coils surrounding the armature andmounted on molded bobbins fitting between said pole pieces and means forresiliently supporting said armature.

5. In a loud speaker mechanical transformer. the combination of anarmature, a movable member, an actuating member connecting said armatureto said movable member, the joint between said actuating member andmovable member being formed by extruding the metal of said movablemember to form a cylindrical opening into which said actuating member isriveted and soldered.

